Since 2016 [1]}, numerous experimental results have been reported on the photoluminescent properties of the single-photon emitters at \(\sim \) 2 eV in hBN [2]}, [3]}, [4]}, [1]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, [13]}, [14]}, [15]}, [16]}, [17]}, [18]}, [19]}, [20]}, [21]}, [12]}.
In TABLE REF , we summarize the range and averaged values of photoluminescent properties observed in experiments, including the zero-phonon line (ZPL), phonon-sideband energy (PSE), Huang-Rhys factor (HR factor), and the photoluminescence lifetime (\(\tau ^{PL}\) ). Typically, a \({\sim }2\)  eV single-photon emitter in hBN exhibits a photoluminescence (PL) spectrum comprised of a sharp ZPL and one or two moderate phonon-sidebands (PSB) at room temperature. The PSE is the energy separation between the ZPL and the first PSB peak. The electron-phonon coupling is estimated by either HR factor (\(S\) ) or Debye-Waller (DW factor\(=e^{-S}\) ) [23]}. The HR factor is typically \(\sim \) 1, which indicates weak electron-phonon coupling. Furthermore, the PL lifetime is on the order of a few ns, and quantum yield (QY, \(\eta \) ) is reported to be \(6{\sim }12\) % [24]}. PL lifetime (\(\tau ^{PL}\) ) reflects the lifetime of an excited state, determined by radiative (\(\tau ^{R}\) ) and nonradiative recombination together (\(\tau ^{NR}\) , \(\tau ^{PL}=1/(1/\tau ^{R}+1/\tau ^{NR})\) ). On the other hand, QY (\(\eta \) ) reflects the proportion of radiative recombination rates with respect to the total recombination rates, and is related to PL lifetime through \(\tau ^{PL}=\tau ^{R}*\eta \) . PL lifetime and QY underscore the importance of studying both radiative and nonradiative recombination lifetimes.
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